This invention relates generally to an apparatus and method for removing plastic compounds that encapsulate integrated circuits and particularly, to a laser-equipped apparatus and method for decapsulating plastic encapsulated integrated circuits.
The vast majority of integrated circuits are packaged in plastic resins including but not limited to biphenyl, ortho-cresol novolac, and dicyclopentadienyl types. The plastic package seals the enclosed integrated circuit from the external environment, including moisture and dust. The resin contains fillers such as silica or other insulating materials to enhance the physical and mechanical properties of the package. The integrated circuits are encapsulated using a transfer molding process. During that process a solid charge of resin is melted and then forced under pressure into a multi cavity mold that contains a number of integrated circuits. One mold may contain tens or hundreds of integrated circuits. The size of the molded integrated circuits varies in length, width and height. As the resins cool, their molecules cross-link into a solid resin. Some devices using the standard dual-in-line package are several millimeters thick. Other small outline packages are a millimeter in thickness.
There are a number of reasons for removing the plastic encapsulant from finished Integrated circuits. One reason is to monitor the manufacturing process. In most mass manufacturing processes, samples of finished product are often taken and analyzed to check whether or not the finished product is made to the manufacturing specifications. When one or more devices fail, it is desirable to analyze those failed devices to detect process flaws so that the flaws can be corrected. Some devices are also reverse engineered in order to discover how the device is constructed.
Current techniques for removing the plastic are time consuming and environmentally unfriendly. One acid etching technique uses fuming nitric or sulfuric acid. That technique can take several hours or more to remove the plastic, and the spent chemicals must be properly disposed of. In addition, these harsh chemicals come in contact with the surface of the integrated chip being exposed, which may chemically remove foreign substances or contaminants residing between the top of the die and the mold compound which will subsequently not be detected in failure analysis. Plasma etching may be used but it is slow and also leaves undesired residues. As such, there is a long felt and unfulfilled need for a faster process that is environmentally friendly and less disruptive to the top surface of the integrated circuit chip.